Multiple sheet misfeeds are a common problem associated with sheet media feeding systems used with printers, copiers and the like. As the top sheet is "picked" from the stack of sheet media in the input tray, the next-to-top sheet, or top few sheets, are sometimes drawn partially into the feed mechanism by frictional forces between the top "fed" sheet and those beneath it. If these sheets are not cleared from the feed zone, then multiple sheets are likely to be drawn fully into the feed zone during the next pick cycle, resulting in a misfeed. One mechanism for reducing misfeeds is described in U.S. Pat. No. 5,269,506 entitled "Paper Pick-up System for Printers", issued Dec. 14, 1993 to Olson et al. and subject to common ownership herewith. The system described therein includes a pivotally operable, spring returnable separator located adjacent to and beneath the infeed rollers of the sheet pick mechanism. The separator has a frictionally adherent pad that opposes advancement of a next-to-top sheet in the infeed paper stack while the top sheet of the stack is pulled thereacross by one or more rollers. Although such a separator pad may be effective in opposing advancement of a next-to-top sheet fully into the feed zone, there typically remains undesirable advancement of the sheets below the top sheet partially into the feed zone. In addition, next-to-top sheets must be cleared from the separator pad so that a sufficient frictional area of the pad remains exposed for separation during the next pick/feed cycle.
Another mechanism for reducing multiple sheet misfeeds is disclosed in U.S. Pat. No. 5,316,285, issued to Olson et al. on May 31, 1994, and subject to common ownership herewith. Described therein is a realignment lever located adjacent to and beneath the sheet feeding rollers. At the beginning of the sheet feeding cycle, the realignment lever is moved out of the feed zone. After the top sheet is picked and passes by the lever, the lever is urged by spring force through the feed zone toward its rest position against the leading edge of the stack of sheets in the input tray. As the lever moves through the feed zone, it urges away from the feed zone any sheets that may have been partly advanced toward the feed zone. Under some conditions, such as a high angle input tray, a high humidity operating environment or lightweight sheet media, and particularly for those feed systems that utilize a frictionally adherent separation pad, the media will resist the return force and thereby increase the number of multiple sheet misfeeds. Increasing the return spring force can damage the leading edge of some sheet media and allows postcard type media to jump up and down in the input tray.